The present invention is related to subsurface tissue blood flow imaging techniques. More particularly, the invention is based on a new highly efficient technique based on coherent laser light speckle contrast (SC) and diffuse correlation tomography.
Imaging blood flow is critical to the diagnosis and monitoring of many diseases. Examples include most obviously the imaging of cerebral blood flow (CBF) for stroke and other ischemic injuries—all hemodynamic derangements—and also neurodegenerative diseases such as Alzheimer's.
Coherence optical measures have traditionally had a role in rodent stroke studies by way of the laser Doppler flowmetry point measurement technique. Areas of high blood flow increase the Doppler broadening of coherent laser light. However, laser Doppler methods are point measures that rely on single scattering with limited depth penetration (<1 mm). Laser Doppler methods can be extended to imaging by raster scanning the Laser Doppler probe, but this is very slow.
Speckle methods monitor blood movement through measures like the speckle contrast related to the intensity autocorrelation function, C(τ), of coherent laser speckle. The speckle contrast will decay more quickly in tissue with tissue with faster blood flow.
There are three distinct speckle measurement approaches including: spectral (laser Doppler, LD) temporal (correlation spectroscopy) and spatial (speckle contrast). Traditional LD analysis monitors the C(T) by looking at Doppler broadening of speckle in the light frequency domain. Spatial methods monitor an integrated measure, by temporally integrating the intensity of many spatially distinct speckles for a fixed time (with a CCD for example) and performing a spatial statistical analysis.
In US 2012/0095354 Dunn et al describes laser speckle contrast imaging. However Dunn et al. presents many limitations, like noise, and is not suitable for 3D imaging.